You can make John McCain’s task tonight really complex, expecting him to introduce many new lines of attack, respond to every thrust, pirouette, change his personality, etc.

Or you can put things very simply: every minute he failed to clearly and convincingly separate himself from President Bush, he was losing. During the past two weeks, the bottom has fallen out of the Republicans’ ability to woo swing voters. It’s about the economy, and the assumption that Bush is responsible for it. Having missed the best opportunity to staunch the bleeding — returning to Washington to lead the congressional opposition to the bailout plan, proposing a better alternative and demanding that an unpopular president embrace it — McCain must now seek every rhetorical opportunity to distance himself from Bush.

Sure, the campaign should also try to link Obama to unpopular congressional leaders and radical figures and ideas, but that’s not the fundamental problem. Swing voters are mad and they want to vote against Bush. McCain will do.

For his part, all Obama had to do was avoid making a mistake — you know, by letting his mind wander away from the question onto matters such as who’ll be the deputy Commerce secretary for widget promotion and such.